Two-dimensional, noncontact measurement of the natural frequencies of dragonfly wings using a quadrant position sensor

1995 ◽  
Vol 34 (4) ◽  
pp. 1226 ◽  
Author(s):  
Hirokazu Matsumoto
Keyword(s):  
Natural Frequencies ◽  
Position Sensor ◽  
Two Dimensional ◽  
Noncontact Measurement ◽  
Dragonfly Wings

scholarly journals A space structural mechanics model of silicene

2020 ◽  
Vol 234 (1-2) ◽  
pp. 3-10
Author(s):  
Mohsen Motamedi
Keyword(s):  
Natural Frequencies ◽  
Strain Curve ◽  
Structural Mechanics ◽  
Dynamics Simulation ◽  
Mode Shapes ◽  
Two Dimensional ◽  
Stress Strain Curve ◽  
Beam Elements ◽  
Mechanics Model ◽  
Good Agreement

The two-dimensional nanostructures such as graphene, silicene, germanene, and stanene have attracted a lot of attention in recent years. Many studies have been done on graphene, but other two-dimensional structures have not yet been studied extensively. In this work, a molecular dynamics simulation of silicene was done and stress–strain curve of silicene was obtained. Then, the mechanical properties of silicene were investigated using the proposed structural molecular mechanics method. First, using the relations governing the force field and the Lifson–Wershel potential function and structural mechanics relations, the coefficients for the BEAM elements was determined, and a structural mechanics model for silicene was proposed. Then, a silicene sheet with 65 Å × 65 Å was modeled, and Young’s modulus of silicene was obtained. In addition, the natural frequencies and mode shapes of silicene were calculated using finite element method. The results are in good agreement with reports by other papers.

Effects of In-plane Load on Flutter of Homogeneous Laminated Beam Plates with Delamination

2000 ◽  
Vol 123 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Le-Chung Shiau ◽  
Yuan-Shih Chen
Keyword(s):  
Mach Number ◽  
Natural Frequencies ◽  
Plate Theory ◽  
Compressive Load ◽  
Two Dimensional ◽  
Plate Model ◽  
Laminated Beam ◽  
Simply Supported ◽  
Flutter Boundary ◽  
Homogeneous Beam

The effects of in-plane load on flutter characteristics of delaminated two-dimensional homogeneous beam plates at high supersonic Mach number are investigated theoretically. Linear plate theory and quasi-steady supersonic aerodynamic theory are employed. A simple beam-plate model is developed to predict the effects of in-plane load on flutter boundaries for the delaminated beam plates with simply supported ends. Results reveal that the presence of an in-plane compressive load degrades the stiffness and natural frequencies of the plate and thereby decreases the flutter boundary for the plate. However, for certain geometry, the flutter boundaries were raised due to flutter coalescence modes of the plate altered by the presence of the in-plane load on the plate.

scholarly journals High Frequency Modal Testing of the Multiblade Packets Using a Noncontact Measurement and Excitation System

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
C. H. Liu ◽  
C. Zang ◽  
F. Li ◽  
E. P. Petrov
Keyword(s):  
High Frequency ◽  
Measurement Method ◽  
Natural Frequencies ◽  
Spectral Lines ◽  
Modal Testing ◽  
Frequency Resolution ◽  
Mode Shapes ◽  
Finite Model ◽  
Frequency Range ◽  
Noncontact Measurement

High cycle failure of blades and vanes caused by the vibration is one of the major causes reducing the lifetime of turbomachines. For multiblade packets, the failure may occur at vibrations with high frequencies that can reach up to tens of kHz. The experimental modal testing of blades is crucial for the validation of numerical models and for the optimization of turbomachine design. In this paper, the test rig and procedure for measurements of dynamic characteristics of lightweight multiblade packets in wide and high frequency ranges are developed. The measurements are based on a noncontact excitation and noncontact measurement method, which allows the determination of the modal characteristics of the packets with high accuracy in wide frequency ranges. The responses of the multiblade packets are measured using a Scanning Laser Doppler Vibrometry (SLDV), while vibrations are excited by the acoustic excitation technique. Modal tests of the blade packet comprising 18 vane blades connected by shrouds are performed. The measurements are performed within the high frequency range of 0–30 kHz, and the natural frequencies and mode shapes are obtained for first 97 modes. To capture the complex high frequency blade mode shapes, each blade in the packet is scanned over 25 reference points uniformly distributed over the blade concave surface. In order to obtain the high frequency resolution, the frequency range used for the measurements is split into several frequency intervals accordingly to the number of spectral lines available in the used data acquisition system, and for each such interval, the test is performed separately. The finite model of the packet is created, and the numerical modal analysis is performed to compare the calculated natural frequencies and mode shapes with the experimental measurements. The comparison shows the satisfactory with those from finite element analysis. It illustrates the measurement method described in this work is effective and reliable.

Gravity waves in a circular well

2002 ◽  
Vol 460 ◽  
pp. 177-180
Author(s):  
JOHN MILES
Keyword(s):  
Free Surface ◽  
Half Space ◽  
Gravity Waves ◽  
Natural Frequencies ◽  
Single Mode ◽  
Two Dimensional ◽  
Characteristic Determinant ◽  
Parallel Argument ◽  
Single Mode Approximation ◽  
Infinite Reservoir

The natural frequencies of gravity waves in a circular well that is bounded above by a free surface and below by a semi-infinite reservoir are approximated by neglecting the off-diagonal terms of the characteristic determinant (single-mode approximation) and invoking the known results for an aperture in a half-space (well of zero depth). A parallel argument yields the corresponding results for a two-dimensional well (a slot). Comparison with Molin's (2001) numerical results for a slot suggests that the error in the single-mode approximation is [lsim ] 1%.

Development of a two-dimensional fiber optic position sensor

Optik ◽  
2018 ◽  
Vol 169 ◽  
pp. 376-381 ◽  
Author(s):  
Ravi Dhawan ◽  
Biswaranjan Dikshit ◽  
Nitin Kawade
Keyword(s):  
Fiber Optic ◽  
Position Sensor ◽  
Two Dimensional

FREE VIBRATIONS OF COMBINED HEMISPHERICAL–CYLINDRICAL SHELLS OF REVOLUTION WITH A TOP OPENING

2013 ◽  
Vol 14 (01) ◽  
pp. 1350023 ◽  
Author(s):  
JAE-HOON KANG
Keyword(s):  
Present Method ◽  
Thin Shell ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Ritz Method ◽  
Three Dimensional ◽  
Free Vibrations ◽  
Two Dimensional ◽  
Algebraic Polynomials ◽  
Shells Of Revolution

A three-dimensional (3D) method of analysis is presented for determining the free vibration frequencies of joined hemispherical–cylindrical shells of revolution with a top opening. Unlike conventional shell theories, which are mathematically two-dimensional (2D), the present method is based upon the 3D dynamic equations of elasticity. Displacement components ur, uθ and uz in the radial, circumferential, and axial directions, respectively, are taken to be periodic in θ and in time, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the joined shells are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies. Natural frequencies are presented for different boundary conditions. The frequencies from the present 3D method are compared with those from 2D thin shell theories.

Hydrodynamics Loads on Two Degree-of-Freedom Cylinder With Uncertain Natural Frequencies Subject to VIV

2009 ◽  
Author(s):  
Didier Lucor
Keyword(s):  
Natural Frequencies ◽  
Numerical Study ◽  
Spectral Element ◽  
Numerical Approach ◽  
Response Surfaces ◽  
Degree Of Freedom ◽  
Two Dimensional ◽  
Wide Range ◽  
Two Dimensional Flow ◽  
Two Degree Of Freedom

In this numerical study, we build response surfaces of two degree-of-freedom vortex-induced vibrations (VIV) of flexibly mounted cylinders for a wide range of transverse and in-line natural frequencies. We consider both the structure and the flow to be two-dimensional and the structure has a low mass damping. The emphasis is put on the representation of the hydrodynamic loads acting on the cylinder in response to the change in the natural frequencies of the structure. The system is sampled for a wide range of natural frequencies within the synchronization region, totaling 149 two-dimensional flow-structure simulations. The parametric range of the in-line frequency is chosen to be larger than the one of the transverse frequency in order to favor multi-modal responses. No preferred frequencies are emphasized within the intervals of study. The fully spectral numerical approach relies on a stochastic collocation method coupled to a spectral element-based deterministic solver.

In-plane free vibration and stability of rotating annular discs

2002 ◽  
Vol 216 (4) ◽  
pp. 371-380 ◽  
Author(s):  
H R Hamidzadeh
Keyword(s):  
Free Vibration ◽  
Natural Frequencies ◽  
Elastic Stability ◽  
Theory Of Elasticity ◽  
Mode Shapes ◽  
Two Dimensional ◽  
Governing Equations ◽  
Stress Theory ◽  
Rotating Discs ◽  
Annular Disc

The in-plane free vibration in an elastic, isotropic, rotating annular disc is investigated on the basis of the two-dimensional linear plane stress theory of elasticity. An analytical solution of the governing equations is developed. Accurate natural frequencies and mode shapes for several modes at different radius ratios and boundary conditions are determined. The computed results demonstrate the influence of rotational speed and radius ratio on the natural frequencies and elastic stability of the rotating discs for several modes. Comparisons of the results with previously established results indicate excellent agreement.

Effect of a layered environment on the complex natural frequencies of two-dimensional WGM dielectric-ring resonators

2002 ◽  
Vol 20 (8) ◽  
pp. 1563-1572 ◽  
Author(s):  
S.V. Boriskina ◽  
T.M. Benson ◽  
P. Sewell ◽  
A.I. Nosich
Keyword(s):  
Natural Frequencies ◽  
Ring Resonators ◽  
Two Dimensional
Sign in / Sign up

Export Citation Format

Share Document